1. Field of the Invention
The present invention relates to a technique for electrically connecting two mutually isolated circuit layers to each other and, more particularly, to a crimping apparatus and system and method for electrically connecting two mutually isolated circuit layers formed on a flexible printed circuit to each other through mold pressing.
2. Description of the Prior Art
Please refer to FIG. 1A, which illustrates a flexible printed circuit. Generally, the flexible printed circuit 1 comprises an isolation layer 10, a first circuit layer 11, and a second circuit layer 12. The isolation layer 10 is formed from a flexible material and the first and second circuit layers 11 and 12 are respectively formed on upper and bottom surface of the isolation layer 10 whereby the first circuit layer 11 is electrically isolated from the second circuit layer 12. In one specific application, there is a need for electrically connecting the first circuit layer 11 to the second circuit layer 12 which is implemented by a crimping operation where a stress is acted on the flexible printed circuit 1 such that a portion of metal material of the first circuit layer 11 penetrates throughout the isolation layer 10, thereby binding to a portion of metal material of the second circuit layer 12 such that the first circuit layer is electrically connected to the second circuit layer 12.
In the conventional art, the crimping process is performed by using a resilient element for storing a resilient force by which the mold pressing can be operated. Thereafter, the resilient force is released for driving a mold to press the flexible printed circuit 1 whereby the first circuit layer 11 formed on the upper surface of the isolation layer 10 is penetrated throughout the isolation layer 10 and electrically connected to the second circuit layer 12 formed on the bottom surface of the isolation layer 10. In one operation embodiment, such as roll-to-roll manufacturing process, since a plurality of flexible printed circuits are sequentially arranged on the flexible substrate, it is necessary to control a plurality of resilient elements for simultaneously performing the crimping process on the plurality flexible circuits respectively corresponding to the plurality of resilient elements. It is well known that the key for performing crimping process toward a plurality of flexible printed circuits simultaneously is the compression control of the resilient elements, i.e., the height of the pressing mold. However, a compression control for ensuring each resilient element to possess the same compression magnitude at the same time so as to generate the same resilient force for mold pressing is difficult. Accordingly, the consequence of crimping process using resilient elements will induce unstable of electrical conduction between the first and second circuit layers 11 and 12 as well as will cause the difficulties of the same compression magnitude of each resilient element adjusted and tuned by the engineers.
It is also known that the crimping quality depends on the stability control of the compressive stress exerted on the flexible printed circuit 1 during crimping process. If the compressive stress is insufficient, such as the illustration shown in FIG. 1B, the binding force between the first and second circuit layers 11 and 12 is not enough thereby causing circuit layer 11 to break away from the circuit layer 12 in the subsequent manufacturing process and, finally, it will become a defect within the product of the flexible printed circuit after the roll-to-roll manufacturing process. On the contrary, if the compressive stress is excessively applied to the flexible printed circuit, such as the condition shown in FIG. 1C, a damaged portion 13 is easily generated thereby affecting the binding strength and the electrical conduction between the first and second circuit layers 11 and 12. In addition, since there a damaged portion 13 on the flexible printed circuit 1, the upper and bottom molds will mutually contact with each other during the crimping process thereby causing the upper mold to rub against the bottom mold directly so as to reduce the lifetime of the mold.
Accordingly, there is a need for a crimping apparatus and system and method that is insensitive to the pressing height of mold press and to the influence of pressed material and is also easily adjusted by the user for electrically connecting two mutually isolated circuit layers to each other thereby solving the conventional problem of the crimping process.